How to compare two versions of a text and see what changed

How a text comparison works

A diff finds the longest run of content the two versions share, keeps that as unchanged, and marks everything else as removed or added. It does not understand meaning. It only compares characters, so a rewrite that says the same thing in other words shows up as a big change.

Comparing two texts step by step

1. Open the Text Diff Checker. Paste the older version in the first box and the newer one in the second.
2. Pick the level of detail. Line by line suits lists, code and short notes. Word by word suits sentences and paragraphs, where a single changed word would otherwise flag a whole line.
3. Read the result. In line mode, a minus sign means the line exists only in the first text and a plus sign means only in the second. In word mode, removed words appear in square brackets with minus signs and added words in curly brackets with plus signs.
4. Turn on "Show only changed lines" in line mode when you only care about the differences in a long text.

Remove formatting noise first

The most common reason a comparison looks wrong is that the two texts differ only in layout. One might be wrapped at a different width, indented, or have different spacing. Everything then shows as changed.

Two quick fixes help. Tick "Ignore extra spaces" and "Ignore upper and lower case" if only formatting differs. If the texts are wrapped differently, run each through Remove Line Breaks first so each paragraph becomes one line, then compare in line mode.

Comparing lists

For lists, order often does not matter. Sort both lists with the Sort Lines tool before comparing, and the diff will show only the items that were really added or removed. If a list might contain repeats, run Remove Duplicate Lines on each first so a repeated item does not show up as a change.

What a diff cannot do

• It does not detect moved text. A paragraph that moved appears once as removed and once as added.
• It does not know about meaning, tone or formatting such as bold and headings. Only plain text is compared.
• Very large texts are refused rather than freezing the page. For a long document, compare it in sections.

Privacy

The comparison runs in your browser tab, so neither version leaves your device. That makes it suitable for drafts, contracts and other text you would not want to paste into a service that uploads it.